1. Field of the Invention
The invention relates to a terminal stud in the rotor of an electric machine, in particular a turbo-generator, for connecting the exciter supply lead, which extends axially in the center of the rotor, to the exciter winding conductors in the winding overhang of the rotor, which stud is produced from steel and consists of a shank and threads on both stud ends.
The invention refers in this connection to the prior art which emerges, for example, from Swiss Patent 586,966.
2. Discussion of Background
In turbo-generators, the guidance of the exciter leads on the rotor to the rotor winding is generally performed in a central shaft bore-hole. The conductors in the shaft bore-hole are mostly solid and insulated all around. The connection from these centrally guided solid conductors to the rotor winding is produced via terminal studs screwed radially into the solid conductors. Such a stud is the subject matter of Swiss Patent 586,966, for example. In addition to studs of copper or a copper alloy, use has been made in more recent designs of studs made from high-strength steel, which must then be forcibly cooled. Common to all designs is that, in addition to the screwed connection with the solid conductors in the shaft bore-hole, at least one second screwed joint of the stud in the radial shaft bore-hole is regarded as indispensable in order to counter the centrifugal forces acting on the stud.
The second screwed joint is now located in a shaft section which is extremely highly stressed as a consequence of the shaft deflection due to the dead weight of the rotor and to unbalance forces. In the most unfavorable case, it is possible for cracks which can lead to damage to form in the region of the thread in the radial shaft bore-hole.